DETERMINATION OF OXYGENATES IN GASOLINE BY H-1 NUCLEAR-MAGNETIC-RESONANCE SPECTROSCOPY

Oxygenates such as C-1 to C-4 alcohols and ethers like methyl tert-butyl ether (MTBE) and tert-amyl methyl ether (TAME) are being used as octane boosters in motor gasoline. A quick and accurate method using H-1 NMR spectroscopy has been developed for their estimation based on group molecular weight (GMW) calculations. This method involves the identification and quantitation of oxygenates from their respective a carbon group (RO) resonating in the chemical. shift region of 3.0-4.4 ppm, which is free from gasoline resonances. The relative GMW of aromatics (6.5-7.5 and 2.1-3.0 ppm), olefins (4.5-6.5 ppm), oxygenates (3.0-4.4 ppm), and saturates (0.6-2.1 ppm) have been calculated from integral values of their respective regions. The percentage of each oxygenate has been determined from total GMW of sample and relative GMW of oxygenate present in straight-run (SR) and fluid catalytic cracked (FCC) gasolines. The method has also been found to be applicable to samples containing mixtures of oxygenates.